GB Patent Specification 994726 discloses a linear copolymer, derived from the following: (A) at least one diene consisting of 1,3-butadiene or isoprene, and (B) at least one vinyl-substituted aromatic compound. The diene and aromatic compound are randomly distributed in the copolymer, and the diene content of the copolymer is characterized by (1) a cis-1,4 structure of at least 30 percent, and a 1,2 structure not in excess of 12 percent, and where the diene is butadiene or piperylene, or (2) a cis-1,4 structure of at least 70 percent, and a 3,4 structure not in excess of 15 percent, and substantially no 1,2 content, and where the diene is isoprene. An elastomeric copolymer is made by a copolymerization process using a lithium-based catalyst, and should comprise from 10 to 40 weight percent of polymerized vinyl-substituted aromatic compound. During the copolymerization reaction, the monomer ratio is maintained constant by incremental additions of the faster polymerizing diene 25 monomer. The copolymer may be telomerized by the slower polymerizing monomer by continuing the polymerization after the last incremental addition of the faster polymerizing monomer.
European Patent EP 0530795B1 discloses a process for preparing continuously tapered polymers and copolymers having a continuous change in 30 microstructure along the polymer backbone. The process produces polymers and copolymers with multiple glass transition temperatures of very small energy absorption, that is, no definable glass transition temperature. The polymers are disclosed as having a flexible chain end, and as becoming progressively stiffer along the length of the chain.
European Patent EP 0530796B1 discloses a process for the dispersion copolymerization of 35 to 70 percent, by weight, of vinyl substituted aromatic monomer, and 30 to 65 percent, by weight, of conjugated diene monomer. The process comprises carrying out the copolymerization in a reaction mixture containing a liquid aliphatic linear hydrocarbon dispersing medium, an anionic catalyst system, and a block copolymer dispersing agent, comprising at least two polymer blocks. At least one of the polymer blocks is soluble in the dispersing medium, and at least one other of the polymer blocks is insoluble in the dispersing medium. The dispersing agent is disclosed as acting to disperse the random copolymer of vinyl substituted aromatics and conjugated dienes, which is formed in the presence of the dispersing agent.
European Patent EP 0648790B1 discloses a continuous polymerization process for the preparation of a rubbery copolymer, by the non-aqueous dispersion, random polymerization of a mixture of 30 to 65 percent, by weight, of a conjugated diolefin monomer, preferably butadiene, and 35 to 70 percent, by weight, of a vinyl substituted aromatic monomer, preferably styrene. The polymerization takes place in a liquid aliphatic hydrocarbon dispersion medium, with an anionic initiator catalyst system, in the presence of a block copolymeric dispersing agent, which is continuously prepared in-situ. At least one block of the dispersing agent is continuously prepared prior to the dispersion polymerization reaction, and a second block of the dispersing agent and a rubbery copolymer are continuously prepared in-situ during the dispersion copolymerization. The second block of the dispersing agent is disclosed as having the polymer structure of the continuously produced rubber copolymer.
U.S. Pat. No. 6,903,155 B2 discloses tires suitable for bearing heavy loads, and to the use of a rubber composition to form the treads of such tires. The rubber composition comprises the following: an elastomeric matrix comprising a majority of at least one diene elastomer having, at one or more of its chain ends, a functional group, which is active for coupling to a reinforcing white filler; a reinforcing filler comprising at least 50 percent, by weight, a reinforcing white filler; and a reinforcing white filler/functionalized diene elastomer bonding agent.
U.S. Pat. No. 3,094,512 discloses a process for preparing random copolymers of conjugated dienes and vinyl-substituted aromatic compounds; a process for preparing 1,3-butadiene/styrene random copolymers; and a process for preparing isoprene/styrene copolymers. This patent discloses a process for producing such polymers using an organolithium catalyst. The process comprises charging to a polymerization zone, containing a catalyst of the formula R(Li)x (R is a hydrocarbon radical selected from the group consisting of aliphatic, cycloaliphatic, and aromatic radicals) and a hydrocarbon diluent, a conjugated diene of 4 to 5 carbon atoms, and, simultaneously, a vinyl-substituted aromatic hydrocarbon in which the vinyl group is attached to a nuclear carbon atom. The monomers are charged at a rate less than the normal polymerization rate of the system, under the conditions employed.
UK Patent Application GB 2110695A discloses styrene-butadiene copolymers having a high styrene content, and obtained by polymerizing styrene and butadiene in a hydrocarbon solvent, in the presence of an organolithium compound, and, if necessary, a Lewis base, and then coupling the resulting polymer with a tin halide 15 compound. The copolymer contains, in its main chain, at least 30 percent, by weight, of polymer having tin-carbon bonds, and has a bound styrene content of more than 25 percent, by weight, but not more than 60 percent, by weight, and a content of vinyl bonds, in the butadiene portion, of not less than 30 percent, but less than 50 percent.
GB Patent Specification 903,331 discloses a random copolymer containing not more than 2 percent, by weight, of a block copolymer, and which is prepared by charging a conjugated diene, and a vinyl substituted aromatic hydrocarbon to a polymerization zone, containing a hydrocarbon diluent and a catalyst RLix (where x is 1 to 4 and R is an aliphatic, cycloaliphatic or aromatic radical). The monomers are charged at a rate less than the normal polymerization rate, under the conditions employed. The monomers are added at 1/10 to 1/300 of the total charge per minute (that is, in from 10 minutes to 5 hours). The products have a structure which is 5-20 percent vinyl, 30-95 percent cis, and 0-60 percent trans, and they may be rubbery or liquid.
U.S. Pat. No. 6,372,863B1 discloses a process for synthesizing random styrene 30 butadiene rubber comprising the following: (1) continuously charging 1,3-butadiene, styrene, an initiator, and a solvent into a first polymerization zone, (2) allowing the 1,3-butadiene and styrene to copolymerize, in the first polymerization zone, to total conversion of 60 to 90 percent, to produce a polymer cement containing living styrene-butadiene chains, (3) continuously charging the polymer cement and additional 1,3-butadiene monomer into a second polymerization zone, wherein from 20 to 40 percent of the total amount of 1,3-butadiene changed, is charged into the second polymerization zone, (4) allowing the copolymerization to continue in the second polymerization zone, to a conversion of the 1,3-butadiene monomer of at least 90 percent, wherein the total conversion of styrene and 1,3-butadiene in the second polymerization zone is limited to a maximum of 95 percent, (5) withdrawing a polymer cement of random styrene-butadiene rubber having living chain ends from the second reaction zone, (6) killing the living chain ends on the random styrene-butadiene rubber, and (7) recovering the random styrene-butadiene rubber from the polymer cement. The copolymerizations in the first polymerization zone and the second polymerization zone are carried out at a temperature in the range of 70° C. to 100° C., and the amount of styrene charged into the first polymerization zone is at least 5 percent more than the total amount of styrene bound into the rubber.
U.S. Pat. No. 4,845,154 discloses copolymers of aromatic vinyl compounds (for example, styrene) and conjugated diolefins (for example, butadiene), and which possess a differential content of the aromatic vinyl compound, such that, in at least one of the end portions of the copolymer, the differential content shows a sharp and substantial increase in the direction of the outer extremity of the end portion. Preferred copolymers are styrene-butadiene copolymers having a vinyl content of at least 30 percent. In some embodiments, the copolymers have a styrene content changing in a portion of no more than 5 percent of the copolymer chain, from a first value to a second value, and where the second value is at least 25 percentage points 25 greater than the first value, and the portion is present within a 10 percent terminal portion of the copolymer.
GB Patent Specification 1387920 discloses copolymers prepared by simultaneously passing a mixture of styrene and butadiene to a reaction zone, the polymerization being carried out in the presence of a polymeric organodilithium compound (for example, polybutadiene dilithium), suitably in an organic medium. During the reaction, the monomer mixture is added to the polymerization vessel at a rate at least as great as the rate of polymerization, and preferably 5-10 percent greater. The less reactive monomer, styrene, therefore builds up in the reaction mixture, so that it forms an increasing proportion of the polymer towards the chain ends, and forms terminal homopolymer blocks, after cessation of the addition of monomers, and reaction of all the butadiene.
There is a need for new rubber formulations that have an excellent wet grip/rolling resistance/wear and tear properties. There is a further need for new rubbers that can be economically produced, without the need of costly modifiers.